The present invention relates to metal removal systems and methods and, more specifically, to such systems adapted to remove a waste metal from a waste solution containing the waste metal.
In many situations, certain waste materials must be removed from waste solutions before the solution is allowed to flow into public sewer systems. Typically, the waste solutions are created by a processing facility located in a mall or other building connected to the public sewer system and arranged between the processing facility and the sewer system.
The present invention is of particular significance when used to remove metals from waste solutions destined to flow into a public sewer system. A common example would be a photograph processing facility employing a developing process using silver. Other examples would be fixers and other solutions for photographic, X-ray, and lithographic processes and the tailings from electrolytic plating processes. In all of these situations, environmental laws may require the removal of certain metals from the waste solution. And in some situations, such as when silver is used in a photographic process, the metal to be removed may have value.
Accordingly, a number of systems and methods have been developed for removing metal ions such as silver from a waste solution. The present invention relates to such removal systems that are connected between a drain in which the waste solution is disposed and the public sewer system. These systems typically comprise a two-stage filtration system using steel wool as the reaction media. Such removal systems typically employ two interchangeable containers containing steel wool. The waste solution is caused to flow first through one of containers and then through the other of the containers. Usually, the first container in series is removed and returned for processing, the second container in the series is placed first in the series, and a new container is placed second in the series. The returned containers are typically processed at a central location remote from the source of the waste solution to recover the precipitated metal.
Available metal ion removal systems that employ two stage treatment may be too complex for certain users. Such systems require at least a minimum level of expertise, and the potential exists for error in installation and operation of these systems. In addition, the use of two separate containers increases the possibility for leaks.
The need thus exists for an improved system for the removal of metal ions from solutions that is simpler to operate than known metal removal systems.
The Applicant is the named inventor of U.S. Pat. No. 4,842,644 for a silver recovery method. The ""644 patent discloses a single stage filtration process in which a waste solution is forced upwards through a reaction media that removes silver from the waste solution.
The following references were uncovered as part of a professional patentability search conducted on behalf of the Applicant:
U.S. Pat. No. 6,200,521 discloses a two-stage waste recovery system for removing silver from a waste solution; only one of the reaction stages is silver reactive.
U.S. Pat. No. 6,096,209 to O""Brien et al. discloses a three media silver recovery apparatus in which the three media are arranged in series within a single container.
U.S. Pa. No. 5,900,041 to Riviere et al. discloses a metal recovery system that intermingles a reactive media such as strands of steel wool with a support structure of an inert material to encourage non-channeling random flow paths.
U.S. Pat. No. 5,837,188 to Peterson discloses a silver recovery system employing a single silver reactive stage.
U.S. Pat. No. 5,641,452 to Azzara discloses a silver recovery system having an outer container and a silver recovery cartridge formed by a liner containing a reactive material.
U.S. Pat. No. 5,603,890 to Fuller discloses a silver recovery device having a hollow core of reactive material arranged within a container. Fluid flows into the container and then laterally through the hollow core to an outlet pipe arranged at the center of the core.
U.S. Pat. No. 5,472,176 to Azzara discloses a silver recovery device employing an inner chamber and an outer chamber. The inner chamber contains a reactive media; the waste solution flows down through the reactive media and into the outer chamber and then up to an outlet.
U.S. Pat. No. 5,458,024 to Schiller et al. discloses a silvery recovery system having a fiber pads arranged above and below a reactive media.
U.S. Pat. No. 5,310,629 to McGuckin et al. discloses a silver recover element in the form of a cylindrical flow-through cylinder having a hollow core and an external substrate layer containing physical development nuclei.
U.S. Pat. No. 5,298,170 to Woog discloses a device defining a chamber in which spent photographic developer and fixer is mixed and neutralized. The waste solution is passed through a vertical conduit containing iron and then across steel wool at the bottom of the device.
U.S. Pat. No. 5,229,009 to Woog discloses a mixing chamber having a length of ribbon defining a tortuous flow path to encourage mixing of photographic developer and fixer as they flow through reactive material within the chamber.
U.S. Pat. No. 5,173,247 to Woog discloses a silver recovery device using plastic chips to stabilize scrap metal within a container.
U.S. Pat. No. 5,112,390 to MacKay discloses a single stage silver recovery system having a replaceable core.
U.S. Pat. No. 4,854,552 discloses a silver recovery system employing steel wool in a vessel with a metal salt of copper or cadmium.
U.S. Pat. No. 4,662,613 to Woog discloses a reusable metal recovery cartridge having a housing that contains a spiral rolled exchange mass containing particles of the recovery media.
U.S. Pat. No. 4,523,993 to Farber discloses a silver recovery system comprising an outer vessel and a perforated inner vessel containing reactive media. The waste solution is poured into the inner vessel as the inner vessel is rotated to encourage desirable flow through the reactive media.
U.S. Pat. No. 4,441,697 to Peterson et al. discloses a silver recovery unit having an elongate core and an aperture in the side thereof. Inner and outer reactive media are arranged within the core on either side of a baffle to enhance the flow path through the unit.
U.S. Pat. No. 4,331,472 to King, Jr. discloses a metal removal apparatus and method employs buoyant elements comprising a substrate coated with a reaction media.
U.S. Pat. No. 4,325,732 to Woog discloses a silver recovery cartridge containing a rolled mat to which a silver reactive material is adhered.
U.S. Pat. No. 4,240,617 to MacKay discloses a cartridge for recovering silver comprising a spiral rolled iron window screen. The waste solution flows down through the screen and then up through an outlet tube extending down the middle of the rolled window screen.
U.S. Pat. No. 4,213,600 to Thompson, Jr. discloses a silver reclamation system comprising reactive and non-reactive layers arranged in successive layers within a housing.
U.S. Pat. No. 3,840,217 to MacKay discloses a silver recovery system employing a woven screen of a reactive material that is wound upon itself to form a reactive media that precipitates silver.
U.S. Pat. No. 3,744,995 to MacKay discloses a silver recovery system comprising a metallic core of window screen that allows transverse flow.
U.S. Pat. No. 3,655,175 to Zeleny et al. discloses a process for recovering metal from a solution in which the housing is disposed of during the recovery process.
U.S. Pat. No. 3,369,801 to Hartman discloses a silver recovery system that forces waste solution down through an inlet pipe, up through a reactive media, and then out through an annular chamber defined by an outlet pipe surrounding the inlet pipe.
U.S. Pat. No. 3,792,845 to Larson et al. discloses a silver recovery cartridge comprising an outer container having a drum, a lid, and a rim clamp that secures the lid on the drum.
U.S. Pat. No. 2,905,323 to Megesi discloses a silver recover system comprising a housing divided into upper, middle, and lower sections by two perforated plates. The recovery media is located within the middle sections. A pipe allows fluid to bypass the middle section when the recovery media becomes clogged.
The present invention may be embodied as a removal system for removing a waste metal from a waste solution. The removal system comprises outer and inner containers and inlet, intermediate, and outlet conduits. The outer container defines an outer chamber, and the inner container defines an inner chamber. The inner container is located within the outer chamber. The inlet conduit allows fluid to flow from an exterior of the outer container to the inner chamber. The intermediate conduit allows fluid flow from the inner chamber to the outer chamber. The outlet conduit allows fluid flow from the outer chamber to the exterior of the outer chamber. A first reaction media is located in the inner chamber, and a second reaction media is located in the outer chamber. In use, the waste solution is forced along a removal path through the inlet conduit, the first reaction media, the intermediate conduit, the second reaction media, and the outlet conduit.